Computational study of the working mechanism and rate acceleration of overcrowded alkene-based light-driven rotary molecular motors
2014 (English)In: RSC Advances, ISSN 2046-2069, Vol. 4, no 20, 10240-10251 p.Article in journal (Refereed) Published
In recent years, much progress has been made in the design, synthesis and operation of light-driven rotary molecular motors based on chiral overcrowded alkenes. Through consecutive cis–trans photoisomerization and thermal helix inversion steps, where the latter dictate the overall rate of rotation, these motors achieve a full 360° unidirectional rotation around the carbon–carbon double bond connecting the two (rotator and stator) alkene halves. In this work, we report quantum chemical calculations indicating that a particularly fast-rotating overcrowded alkene-based motor capable of reaching the MHz regime, can be made to rotate even faster by the substitution of a rotator methyl group with a methoxy group. Specifically, using density functional theory methods that reproduce the rate-limiting 35 kJ mol−1 thermal free-energy barriers shown by the methyl-bearing motor with errors of 5 kJ mol−1 only, it is predicted that this substitution reduces these barriers by a significant 15–20 kJ mol−1. This prediction is preceded by a series of benchmark calculations for assessing how well density functional theory methods account for available experimental data (crystallographic, UV-vis absorption, thermodynamic) on the rotary cycles of overcrowded alkenes, and a detailed examination of the thermal and photochemical reaction mechanisms of the original motor of this type.
Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014. Vol. 4, no 20, 10240-10251 p.
IdentifiersURN: urn:nbn:se:liu:diva-104688DOI: 10.1039/C3RA46880AISI: 000332061300048ScopusID: 2-s2.0-84894247198OAI: oai:DiVA.org:liu-104688DiVA: diva2:698493